Re: [PATCH v2 4/4] tools/hotplug: modify set_mtu() to inform the frontend via xenstore

[Ian Jackson <ian.jackson@citrix.com>]

Paul Durrant writes ("[PATCH v2 4/4] tools/hotplug: modify set_mtu() to inform the frontend via xenstore"):
> From: Paul Durrant <pdurrant@amazon.com>
> 
> set_mtu() currently sets the backend vif MTU but does not inform the frontend
> what it is. This patch adds code to write the MTU into a xenstore node. See
> netif.h for a specification of the node.
> 
> NOTE: There is also a small modification replacing '$mtu' with '${mtu}'
>       for style consistency.
> 
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>

Reviewed-by: Ian Jackson <ian.jackson@eu.citrix.com>

> diff --git a/tools/hotplug/Linux/xen-network-common.sh b/tools/hotplug/Linux/xen-network-common.sh
> index 37e71cfa9c..24fc42d9cf 100644
> --- a/tools/hotplug/Linux/xen-network-common.sh
> +++ b/tools/hotplug/Linux/xen-network-common.sh
> @@ -164,9 +164,21 @@ remove_from_bridge () {
>  set_mtu () {
>      local bridge=$1
>      local dev=$2
> +    local type_if=$3
> +
>      mtu="`ip link show dev ${bridge}| awk '/mtu/ { print $5 }'`"
>      if [ -n "$mtu" ] && [ "$mtu" -gt 0 ]
>      then
> -            ip link set dev ${dev} mtu $mtu || :
> +            ip link set dev ${dev} mtu ${mtu} || :
> +    fi
> +
> +    if [ ${type_if} = vif ]
> +    then
> +       dev_=${dev#vif}
> +       domid=${dev_%.*}
> +       devid=${dev_#*.}
> +
> +       XENBUS_PATH="/local/domain/$domid/device/vif/$devid"
> +       xenstore_write "$XENBUS_PATH/mtu" ${mtu}

It's surprising to me that this code doesn't have the xenbus path
already in some variable.  But I guess from the fact that you've added
this code, that it doesn't.

Ian.